This program project application is for basic and clinical research related to the effects of HIV infection on pregnant women, the vertical transmission of HIV infection from mother to infant, and the prospective evaluation of infants born to HIV infected women with special attention directed towards the definition of factors which discriminate between HIV infected and uninfected infants. The mother/fetal/placental/infant unit will be followed prospectively from the time the HIV infected pregnant women is identified in the community. Four groups of mothers and their infants will be enrolled: intravenous drug using (IVDU) HIV positive mothers, intravenous drug using (IVDU) HIV negative mothers, non-IVDU HIV negative normal mothers,HIV positive heterosexual consorts. The project includes a core component to support four research projects: 1. studies of cofactors (i.e., herpes viruses, HTLV-I, human papilloma virus) and their impact on the immune system, to assess their role in altering HIV disease progression in the mother, risk of vertical transmission to the fetus, as well as the development of clinical disease in the infant; II. immunologic, virologic and immunohistologic studies of in utero HIV transmission to the fetus to assess the time(s) during pregnancy and the pathogenesis of vertical transmission, as well as the impact of abortion on the progression of clinical AIDS in the mother; III. studies of the placenta and HIV infection to assess the HIV infectivity of the placenta, as well as its role in vertical transmission; IV. definition of the natural history of HIV infection in maternal-infant pairs with special emphasis on factors which promoter progression to clinical disease in HIV-infected mothers and factors which discriminate HIV- infected from uninfected infants born to these mothers. The Core component is structured both to support the individual research projects and to allow for the prospective clinical/virologic/immunologic evaluation of the mother/fetus/placenta/infant unit. The Core component consists of an administrative core unit(A) to support the four research projects; (B) the patient accrual, and epidemiology core will provide the recruitment of the HIV-infected mother as well as the identification of placentas and fetuses to allow for completion of the related research projects: (C) the research laboratory core will consist of immunology, virology and immunohistopathology components to support the four research projects and to allow for the correlation of results with virologic/immunologic status at specified time points. The integration of these research resources provides a strong program with balance between clinical and basic science investigation. Each of the research projects will make use of the Core resources to develop data and to improve our understanding of the effect of HIV infection in maternal-child health.